The present invention is directed to hydrostatic release mechanism for use in a well tool having a hydraulic piston and cylinder assembly which is required to be equalized.
The problem the present invention overcomes is that actuating piston and cylinder assemblies used in well tools, such as safety valves, require a seal which equalizes pressure between the hydrostatic operating pressure and the well pressure when the valves are closed, due to fail safe requirements. For example, see U. S. Pat. Nos. 4,161,219; 4,569,398; RE. 32,390; and 4,660,646; which illustrate various types of seals and sealing valves which provide relatively small areas for limiting the force caused by the hydrostatic pressure thereby allowing the well tools to be used at greater depths. Small seals or sealing valves require small piston mechanism components which are susceptible to damage. That is, the small piston rods, which were subject to the full actuating loads of the piston and cylinder assemblies, are subject to failure. Because of the relatively high loads involved to actuate the sealing area, the seal area components have to thereby be large, consequently increasing the piston rod area, thereby limiting the hydrostatic pressure that it could equalize against, and thereby further limiting the depth at which the safety valve could be used.
The present hydrostatic release means isolates the piston and cylinder assembly loads from the sealing area. The present invention allows the sealing area to be vastly reduced from the prior art designs without further reducing the size of the load carrying component. This allows the sealing area to equalize against greater hydrostatic head pressures and thus allows the well tool to be set at a greater depth.